Conventionally, there has been a refrigerating apparatus disposed with a vapor compression-type refrigerant circuit including a heat exchanger configured such that refrigerant flows in from below and flows out from above as an evaporator of the refrigerant (e.g., see Japanese Patent Application Publication No. S63-204074). In order to prevent refrigerating machine oil from accumulating inside the evaporator, the refrigerating apparatus is configured to extract, from the vicinity of the surface of the refrigerant, the refrigerating machine oil accumulating in a state where it floats on the surface of the refrigerant as a result of the refrigerating machine oil and the refrigerant separating into two layers because the specific gravity of the refrigerating machine oil is smaller than that of the refrigerant, and to return the refrigerating machine oil to the intake side of the compressor.
Further, as an example of a refrigerating apparatus disposed with a vapor compression-type refrigerant circuit, there is an air conditioner that is capable of a simultaneous cooling and heating operation and is disposed with a vapor compression-type refrigerant circuit capable of switching that causes heat source heat exchangers and utilization heat exchangers to function separately as evaporators or condensers of the refrigerant (e.g., see Japanese Patent Application Publication No. H03-260561). In this air conditioner, plural heat source heat exchangers are disposed, and expansion valves are disposed such that they can regulate the flow rate of the refrigerant flowing into the heat source heat exchangers. Additionally, in this air conditioner, when the heat source heat exchangers are caused to function as evaporators during a heating operation or during the simultaneous cooling and heating operation, for example, control is conducted to reduce the evaporating ability by reducing the openings of the expansion valves as the air conditioning load of the utilization heat exchangers becomes smaller. Moreover, when the air conditioning load of the utilization heat exchangers becomes extremely small, control is conducted to reduce the evaporating ability by closing some of the plural expansion valves to reduce the number of heat source heat exchangers functioning as evaporators or to reduce the evaporating ability by causing some of the plural heat source heat exchangers to function as condensers to offset the evaporating ability of the heat source heat exchangers functioning as evaporators.
Further, in the aforementioned air conditioner, when the heat source heat exchangers are caused to function as condensers during a cooling operation or during the simultaneous cooling and heating operation, for example, control is conducted to reduce the condensing ability by increasing the amount of liquid refrigerant accumulating inside the heat source heat exchangers and reducing the substantial heat transfer area by reducing the openings of the expansion valves connected to the heat source heat exchangers as the air conditioning load of the utilization heat exchangers becomes smaller. However, when control is conducted to reduce the openings of the expansion valves, there has been the problem that there is a tendency for the refrigerant pressure downstream of the expansion valves (specifically, between the expansion valves and the utilization heat exchangers) to drop and become unstable, and control to reduce the condensing ability of the heat source heat exchangers cannot be stably conducted. In order to counter this problem, control has been proposed to raise the refrigerant pressure downstream of the expansion valves by disposing a pressurizing circuit that causes high-pressure gas refrigerant compressed by the compressor to merge with refrigerant whose pressure has been reduced in the expansion valves and is sent to the utilization heat exchangers (e.g., see Japanese Patent Application Publication No. H03-129259).